In recent years, microchannel chips have been in use for the high-precision and high-speed analysis of trace substances such as proteins and nucleic acids. The microchannel chips have advantages in that even a small amount of reagent or sample suffices, and thus use in various applications such as clinical inspection, food inspection, and environmental inspection are expected.
The microchannel chip has a channel, a chamber, and the like, and a liquid can be moved in the channel on the basis of a capillary phenomenon. In a case where the width of the channel of the microchannel chip is sufficiently narrow, the speed of movement of the liquid is almost the same in a central part and both end parts in the width direction of the channel. In a case where the width of the channel is wide to some extent, the speed of movement of the liquid differs substantially at the central part and both of the end parts in the width direction of the channel. Therefore, in a case where the width of the channel is wide to some extent, the speed of movement of the liquid is not uniform so bubbles remain in the channel.
In order to solve the problem, a microchannel chip whose depth is different in a central portion and both end parts in the width direction of a channel has been proposed (for example, refer to PTL 1). The microchannel chip described in PTL 1 has a pair of grooves formed in the depth direction at both of the width-direction end parts of a bottom surface of the channel which is formed on a substrate formed of resin. The pair of grooves reduce the resistance with respect to a liquid moving through both of the width-direction end parts of the channel and increase the speed of movement of the liquid moving through both of the width-direction end parts of the channel. In the microchannel chip described in PTL 1, the speed of movement of the liquid can be uniform to some extent at the central portion and both of the end parts in the width direction of the channel, and thus bubbles can be prevented from remaining in the channel.